Implicit and explicit reward learning in chronic nicotine use.

BACKGROUND: Chronic tobacco use is related to specific neurobiological alterations in the dopaminergic brain reward system that can be termed "reward deficiency syndrome" in dependent nicotine consumers. The close linkage of dopaminergic activity and reward learning led us to expect implicit and explicit reward learning deficits in dependent compared to non-smokers. Smokers who maintain a less regular, occasional use may also, to a lesser extent, show implicit reward learning deficits. The purpose of our study was to examine the behavioral effects of the neurobiological alterations on reward related learning. We also tested whether any deficits observed in an abstinent state are also present in a satiated state.

METHODS: In two studies, we examined implicit and explicit reward learning in smokers. Participants were administered a probabilistic implicit reward learning task, and an explicit reward- and punishment-based trial-and-error learning task. In Study 1, we compared dependent, occasional, and non-smokers, and in Study 2 satiated and abstinent smokers.

RESULTS: In Study 1, chronic and occasional smokers showed impairments in both, implicit and explicit reward learning tasks. In Study 2, satiated smokers did not perform better than abstinent smokers.

CONCLUSIONS: The results support the hypothesis of reward learning deficits. These deficits are not limited to explicit but extend to implicit reward learning and cannot be explained by tobacco withdrawal.